Running a 12 V battery / inverter system for a secondary power system in a truck?

Discussion in 'General Electronics Chat' started by cyborgemu, Mar 17, 2016.

  1. cyborgemu

    Thread Starter New Member

    Mar 17, 2016
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    I'm on week 5 of a multi-year camping trip in North America. I'm able to make this trip because I do freelance writing work from the laptop, which can be done anywhere with an internet connection, and in many cases, places without.

    My base of operations is a 1993 4runner, and my primary laptop is a Lenovo Y500 that pulls 30-100 W. The transformer block puts out 19.5 V @ 6.15 A. I want to built a 5V power supply (detailed in another thread), and in addition to the 5V, I want to build a secondary 12V system separate from the main car battery. I'm thinking of getting a 100 Ah deep cycle battery with a 600 - 1000 W pure sine inverter to power the laptop transformer, a rice cooker (450 W), and possible eventually a 120V / 12V fridge/freezer.

    A couple questions:

    - I've already spent several hours researching inverter / battery combinations and I'm still not sure what's the best buy. I was looking at two 600 W inverters:

    http://www.amazon.com/dp/B00AYH6BSO/
    http://www.amazon.com/dp/B003FWNWN2/

    and two 100 Ah batteries:

    http://www.amazon.com/dp/B00S2MDZFK/
    http://www.amazon.com/dp/B00S1RT58C/

    And additionally I want to buy a battery monitor (http://www.amazon.com/dp/B013PKYILS/ ?) and get the right kinds of cables (4 AWG?) and I'd love to install a relay shunt that I can toggle so that if the main car battery dies I can connect the two 12V systems and start the car off the secondary system.

    So what do yall think of these selections? Do I need inline fuses? If I'm going to be expanding in the future should I jump for a 1000 W inverter system? Are the pure sine Samlex inverters overkill? Would it be worth trying to wire up an arduino control circuit for this plus the 5 V system? Is this all crazy?
     
  2. tcmtech

    Well-Known Member

    Nov 4, 2013
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    For the laptop I would just get a universal 12 volt automotive laptop power adapter unit for it and save the waste of energy being done in a needless step up and then step back down process. That might set you back $20 at worst if you know where to shop.

    As for the cooker being it's likely just a heating element it won't gain a thing from running from a sine wave inverter VS a modified sine wave unit.

    Same with a 120/12 dual voltage refrigerator. If it has a 12 volt input running off of a inverter to take the voltage up to 120 does not gain a thing either.

    Battery monitors and isolation from the main starting battery for this sort of stuff is always a good idea though so that I agree with.
     
    Last edited: Mar 17, 2016
  3. wayneh

    Expert

    Sep 9, 2010
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    I'd power the laptop from a normal (cheap) DC-to-AC inverter. I've done it with a half dozen laptops without issue, and my inverter is just a cheap "modified sine", meaning it is a nearly square wave that takes a brief rest at 0V as it passes from negative to positive. Nothing fancy, and maybe $30. I chose it because its fan is relatively quiet. It also has a USB port.

    Ditto tcmtech's comments on the appliances. Use straight 12V if that's an option.

    I see your biggest challenge is properly arranging things so that you can charge your extra battery but not use it for starting, except under rare circumstances. I'd be tempted to use a manual option for that. Just move the cable to the backup battery if you need an emergency start. Boat owners frequently set up a system like you're describing. If you want a switch, instead of my manual move-the-cable idea, you might look at what those folks use.

    If you want to go crazy on a battery, take a look at these. Common in boats, for the vibration resistance.
     
  4. tcmtech

    Well-Known Member

    Nov 4, 2013
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    My recommendation for what battery would be good for regular deep cycle work would be a common group 31 size deep cycle Interstate battery.

    It's all we use on our farm equipment now and our oldest ones are pushing 11 years and still working well which is not bad for a ~$130 battery.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    FWIW, the batteries that Interstate markets are made by Johnson Controls, the same company that makes the Optima batteries I linked to, as well as 47% of all automotive batteries in the U.S. The next largest, Exide, went bankrupt again recently when Walmart dropped them.
     
  6. Roderick Young

    Member

    Feb 22, 2015
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    168
    I'm not a big fan of using inverter electricity to heat. That wastes a lot of energy. If you only have the laptop and such as loads, your system can be light-duty, and you can get away with small wires, and possibly less battery. You could use propane to cook. Or you could be alternative, and have a solar cooker, or cook foil-wraps on the truck manifold if you're driving long distances.

    Only you can say, but you may find that you want a reliable internet connection after a while, especially if it is your livelihood, and might wish to invest in a cell phone plan that allows you to tether your laptop.

    Finally, if you ever pass through the San Jose, California area, please message me. I'd love to see your rig.
     
  7. cyborgemu

    Thread Starter New Member

    Mar 17, 2016
    4
    0
    Some great suggestions, many thanks. It's a bit hard to do battery research since there's so many stories, good and bad, for so many of the different models and brands. I definitely want something that'll last, but I'm also hesitant to drop $300 on just a battery.

    Roderick: I love the idea of cooking foil packets on the manifold. Almost all I've been eating are wood campfire foil packets. I do actually have tethering, but most of where I've been camping (desert and mountains of NM and AZ) there's zero cell signal, so that doesn't help me there. Once I get to the coast I bet most of those problems will disappear. Incidentally I'll be up in San Jose / bay area probably early May. Would love to meet up. And if you have any special camping (or sushi) spots, I'm all ears!
     
  8. wayneh

    Expert

    Sep 9, 2010
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    Mmmm... foil packet dinners. One of my faves – grilled cheesy garlic potato packet. :)

    grilled cheesy potato packet.jpg
     
  9. cyborgemu

    Thread Starter New Member

    Mar 17, 2016
    4
    0
    oooh that looks amazing! Share the recipe?

    I've been mostly doing real basic packets with potato / onion / garlic / serrano / carrot / zucchini / butter / salt or hondashi / bacon and then after they come off the coals adding avocado and lime. It's easy but soooo tasty and I can prep 4 meals worth in about 20 minutes at the campsite (building fires isn't included in prep time; that's play, not work). Would love to hear some more ideas for packet combos.
     
  10. wayneh

    Expert

    Sep 9, 2010
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    I use an 8X scaled up version, since making one serving makes no sense to me, but here are links to the (identical) original smaller recipe that may better fit your needs.

    http://www.bettycrocker.com/recipes...to-packs/240ec1a5-5d83-4402-abb3-b2ad3eac6372
    http://www.pillsbury.com/recipes/gr...o-packet/7394d6e1-ebb6-46b7-909f-2cbee275a5f4
    http://www.tablespoon.com/recipes/g...o-packet/1008a511-c950-45e4-998b-1df31d1014ae
     
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